CN112204799A - Lithium ion secondary battery - Google Patents

Lithium ion secondary battery Download PDF

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Publication number
CN112204799A
CN112204799A CN201980028480.3A CN201980028480A CN112204799A CN 112204799 A CN112204799 A CN 112204799A CN 201980028480 A CN201980028480 A CN 201980028480A CN 112204799 A CN112204799 A CN 112204799A
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active material
positive electrode
electrode active
negative electrode
current collector
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Inventor
田名纲洁
田中觉久
青柳真太郎
奥野一树
细江晃久
妹尾菊雄
竹林浩
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Honda Motor Co Ltd
Sumitomo Electric Industries Ltd
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Honda Motor Co Ltd
Sumitomo Electric Industries Ltd
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    • H01M4/64—Carriers or collectors
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    • H01M4/661—Metal or alloys, e.g. alloy coatings
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
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    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H01M4/80—Porous plates, e.g. sintered carriers
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    • H01M4/00—Electrodes
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    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H01M4/80—Porous plates, e.g. sintered carriers
    • H01M4/808—Foamed, spongy materials
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

Provided is a lithium ion secondary battery having excellent energy density and output density and having excellent charge-discharge cycle characteristics. In a lithium ion secondary battery (1), positive electrodes (2) and negative electrodes (3) are alternately adjacent to each other with separators (4, 5) therebetween. The positive electrode (2) comprises a positive electrode current collector composed of a metal porous body, a 1 st positive electrode active material (21) held on one surface of the positive electrode current collector, and a 2 nd positive electrode active material (22) held on the other surface. The negative electrode (3) includes a negative electrode current collector composed of a metal porous body, a 1 st negative electrode active material (31) held on one surface of the negative electrode current collector, and a 2 nd negative electrode active material (32) held on the other surface. The 1 st positive electrode active material (21) faces the 1 st negative electrode active material (31), and the positive electrode active material (22) faces the 2 nd negative electrode active material (32).

Description

Lithium ion secondary battery
Technical Field
The present invention relates to a lithium ion secondary battery.
Background
Conventionally, there is known a lithium ion secondary battery including an electrode on a current collector, the electrode including a 1 st active material layer in which an active material has a particle diameter of 0.1 μm or more and less than 5 μm, and a 2 nd active material layer in which an active material has a particle diameter of 5 to 20 μm, each active material layer having a thickness of 20 to 30 μm (see, for example, patent document 1).
In patent document 1, according to the lithium ion secondary battery including the above-described electrode, the output density can be increased without lowering the energy density.
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent publication No. 2002-151055
Disclosure of Invention
However, the lithium-ion secondary battery described in patent document 1 has a problem that both the energy density and the output density cannot be increased, although the energy density is not reduced.
In order to solve the above problems, the present applicant has proposed a lithium ion secondary battery in which a positive electrode includes a 1 st positive electrode active material layer containing a high capacity type active material formed on a current collector, and a 2 nd positive electrode active material layer containing a high output type active material formed on the 1 st positive electrode active material layer (see japanese patent application No. 2017 and 101887). According to the above lithium ion secondary battery, the energy density can be increased by including the high-capacity active material in the 1 st positive electrode active material layer, and the output density can be increased by including the high-output active material in the 2 nd positive electrode active material layer.
In order to further improve the energy density and output density of a lithium ion secondary battery, a lithium ion secondary battery may be considered in which both a positive electrode and a negative electrode are configured to include a 1 st active material layer containing a high-capacity active material formed on both surfaces of a current collector made of a metal foil and a 2 nd active material layer containing a high-output active material formed on the 1 st active material layer, and the lithium ion secondary battery has a structure in which a plurality of the positive electrodes and a plurality of the negative electrodes are alternately adjacent to each other with separators interposed therebetween.
However, in a positive electrode or a negative electrode including a 1 st active material layer containing a high-capacity active material formed on both surfaces of a current collector made of a metal foil and a 2 nd active material layer containing a high-output active material formed on the 1 st active material layer, there is a problem that the current collector interferes with movement of lithium ions.
Therefore, for example, when lithium ions generated in the 1 st negative electrode active material layer and the 2 nd negative electrode active material layer move to the positive electrode side through the separator interposed between the positive electrode and the negative electrode during discharge, most of the lithium ions are consumed in the 2 nd positive electrode active material layer, and only the remaining lithium ions reach the 1 st positive electrode active material layer and react with the high capacity type positive electrode active material. As a result, the 2 nd positive electrode active material layer becomes resistant to the movement of lithium ions, and the output in the 1 st positive electrode active material layer decreases.
In a lithium ion secondary battery including a 1 st active material layer containing a high-capacity active material formed on both surfaces of a current collector made of a metal foil and a 2 nd active material layer containing a high-output active material formed on the 1 st active material layer, each active material layer is formed by applying a paste containing each active material on the surface of the current collector and drying the paste. Therefore, the thickness of the active material layer is at most about 150 μm, and there is a problem that a sufficient energy density cannot be obtained.
In addition, in a lithium ion secondary battery including a 1 st active material layer containing a high-capacity active material formed on both surfaces of a current collector made of a metal foil on both sides of a positive electrode and a negative electrode, and a 2 nd active material layer containing a high-output active material formed on the 1 st active material layer, since the expansion and contraction rates of the 1 st active material layer and the 2 nd active material layer are different, when charge and discharge are repeated at a high frequency, the interface layer between the 1 st active material layer and the 2 nd active material layer is liable to slip off, and there is a problem that sufficient charge and discharge cycle characteristics cannot be obtained.
The present invention has been made to solve the above problems, and an object of the present invention is to provide a lithium ion secondary battery having excellent energy density and output density and having excellent charge-discharge cycle characteristics.
In order to achieve the above object, a lithium ion secondary battery according to the present invention includes a structure in which at least one positive electrode and at least one negative electrode are alternately adjacent to each other with a separator interposed therebetween, the positive electrode including: a positive electrode current collector composed of a porous metal body having a three-dimensional mesh structure; a 1 st positive electrode active material containing a high capacity type active material held on one surface of the positive electrode current collector; and a 2 nd positive electrode active material containing a high-output type active material and held on the other surface of the positive electrode current collector, wherein the negative electrode includes: a negative electrode current collector composed of a porous metal body having a three-dimensional mesh structure; a 1 st negative electrode active material containing a high-capacity active material and held on one surface of the negative electrode current collector; and a 2 nd negative electrode active material containing a high-output type active material and held on the other surface of the negative electrode current collector, wherein the 1 st positive electrode active material faces the 1 st negative electrode active material adjacent to the negative electrode current collector with the 1 st separator interposed therebetween, and the 2 nd positive electrode active material faces the 2 nd negative electrode active material adjacent to the negative electrode current collector with the 2 nd separator interposed therebetween.
In the lithium ion secondary battery according to the present invention, the positive electrode and the negative electrode each have the porous metal body as a current collector. The porous metal body has a three-dimensional mesh structure in which columnar skeletons are connected three-dimensionally. In the positive electrode, the 1 st positive electrode active material is held on one surface of the current collector, and the 2 nd positive electrode active material is held on the other surface, and in the negative electrode, the 1 st negative electrode active material is held on one surface of the current collector, and the 2 nd negative electrode active material is held on the other surface. As a result, lithium ions can move freely in the positive electrode and the negative electrode without being hindered by the current collector.
Here, the lithium ion secondary battery according to the present invention has a structure in which at least one of the positive electrodes and at least one of the negative electrodes are alternately adjacent to each other with a separator interposed therebetween, and the 1 st positive electrode active material of the positive electrode faces the 1 st negative electrode active material of the negative electrode adjacent to each other with the 1 st separator interposed therebetween, and the 2 nd positive electrode active material faces the 2 nd negative electrode active material of the negative electrode adjacent to each other with the 2 nd separator interposed therebetween.
As a result, the 1 st positive electrode active material can exchange lithium ions with the 1 st negative electrode active material through the 1 st separator, and the 2 nd positive electrode active material can exchange lithium ions with the 2 nd negative electrode active material through the 2 nd separator. In other words, in the lithium ion secondary battery of the present invention, lithium ions can be exchanged between the high capacity type active materials or between the high output type active materials between the adjacent positive electrode and negative electrode.
Therefore, in the lithium ion secondary battery of the present invention, it is possible to suppress a decrease in output, and to add an output generated in parallel by a battery reaction between the high capacity type active materials or a battery reaction between the high output type active materials between the adjacent positive electrode and negative electrode, thereby obtaining an excellent output density.
In the lithium ion secondary battery of the present invention, since the positive electrode active material or the negative electrode active material is held on the porous metal body, one or both of the 1 st positive electrode active material and the 2 nd positive electrode active material can be made 150 μm or more thick in the positive electrode, and one or both of the 1 st negative electrode active material and the 2 nd negative electrode active material can be made 150 μm or more thick in the negative electrode, whereby excellent energy density can be obtained.
In the lithium ion secondary battery of the present invention, since the positive electrode active material or the negative electrode active material is held by the porous metal body, even when charge and discharge are repeated at a high frequency, slipping of the interface layer between the 1 st positive electrode active material and the 2 nd positive electrode active material or the interface layer between the 1 st negative electrode active material and the 2 nd negative electrode active material is suppressed, and excellent charge and discharge cycle characteristics can be obtained.
In the lithium ion secondary battery of the present invention, the high-capacity active material contained in the 1 st positive electrode active material may be Li (Ni)5/10Co2/10Mn3/10)O2、Li(Ni6/10Co2/10Mn2/10)O2、Li(Ni8/10Co1/ 10Mn1/10)O2、Li(Ni0.8Co0.15Al0.05)O2At least one selected from the group consisting of Li (Ni) can be used as the high-output type active material contained in the 2 nd positive electrode active material1/6Co4/6Mn1/6)O2、Li(Ni1/3Co1/3Mn1/3)O2At least one selected from the group consisting of.
In the lithium ion secondary battery of the present invention, the high-capacity active material contained in the 1 st negative electrode active material may be at least one selected from the group consisting of artificial graphite, natural graphite, Si, and SiO, and the high-output active material contained in the 2 nd negative electrode active material may be hard carbon.
Drawings
Fig. 1 is a sectional explanatory view showing one configuration example of a lithium-ion secondary battery of the present invention.
Fig. 2 is a sectional explanatory view showing one configuration example of a conventional lithium ion secondary battery.
Fig. 3 is a graph showing energy density in the lithium-ion secondary battery according to the embodiment of the invention.
Fig. 4 is a graph showing the output density in the lithium-ion secondary battery according to the embodiment of the invention.
Fig. 5 is a graph showing a change in capacity retention rate with respect to the number of cycles in the lithium-ion secondary battery according to the embodiment of the present invention.
Fig. 6 is a graph showing changes in internal resistance with respect to the number of cycles in the lithium-ion secondary battery according to the embodiment of the present invention.
Detailed Description
Next, embodiments of the present invention will be described in further detail with reference to the drawings.
As shown in fig. 1, the lithium ion secondary battery 1 of the present embodiment has a structure in which the same number of 1 st positive electrodes 2 and 1 st negative electrodes 3 are alternately adjacent to each other with 1 st separators 4 or 2 nd separators 5 interposed therebetween, and a 2 nd positive electrode 6 is disposed at one end portion and a 2 nd negative electrode 7 is disposed at the other end portion.
The 1 st positive electrode 2 includes: a current collector not shown; a positive electrode active material 23 composed of a 1 st positive electrode active material 21 containing a high capacity type active material held on one surface of the current collector and a 2 nd positive electrode active material 22 containing a high output type active material held on the other surface of the current collector; and a tab 24 connected to the current collector.
The 1 st negative electrode 3 includes: a current collector not shown; a negative electrode active material 33 composed of a 1 st negative electrode active material 31 containing a high-capacity type active material held on one surface of the current collector and a 2 nd negative electrode active material 32 containing a high-output type active material held on the other surface of the current collector; and a tab 34 connected to the current collector. The current collector of the positive electrode 2 or the negative electrode 3 is composed of a porous metal body having a three-dimensional mesh structure in which columnar skeletons are connected three-dimensionally and having interconnected cells.
The 2 nd positive electrode 6 has exactly the same configuration as the 1 st positive electrode 2, except that the positive electrode active material 23 includes only one of the 1 st positive electrode active material 21 and the 2 nd positive electrode active material 22. Fig. 1 shows a case where the positive electrode active material 23 of the 2 nd positive electrode 6 includes the 1 st positive electrode active material 21.
The 2 nd negative electrode 7 has the same configuration as the 1 st negative electrode 3 except that the negative electrode active material 33 includes only one of the 1 st negative electrode active material 31 and the 2 nd negative electrode active material 32. Fig. 1 shows a case where the negative electrode active material 33 of the 2 nd negative electrode 7 includes the 1 st negative electrode active material 31.
The 1 st positive electrode active material 21 of the 1 st positive electrode 2 faces the 1 st negative electrode active material 31 of the 1 st negative electrode 3 adjacent to the 1 st separator 4, and the 2 nd positive electrode active material 22 faces the 2 nd negative electrode active material 32 of the 1 st negative electrode 3 adjacent to the 2 nd separator 5. In the case where the negative electrode active material 33 of the 1 st negative electrode 3 adjacent to the 2 nd positive electrode 6 via the 1 st separator 4 or the 2 nd separator 5 is the 1 st negative electrode active material 31, the positive electrode active material 23 includes only the 1 st positive electrode active material 21, and in the case where the negative electrode active material 33 is the 2 nd negative electrode active material 32, the positive electrode active material 23 includes only the 2 nd positive electrode active material 22.
Similarly, in the 2 nd negative electrode 7, when the positive electrode active material 23 of the 1 st positive electrode 2 adjacent to each other with the 1 st separator 4 or the 2 nd separator 5 interposed therebetween is the 1 st positive electrode active material 21, the negative electrode active material 33 includes only the 1 st negative electrode active material 31, and when the positive electrode active material 23 is the 2 nd positive electrode active material 22, the negative electrode active material 33 includes only the 2 nd negative electrode active material 32.
The porous metal body constituting the current collector of the positive electrode 2, 6 or the negative electrode 3, 7 is made of a conductive metal such as aluminum, nickel, copper, stainless steel, titanium, etc., and preferably has a porosity of 90 to 98%, a number of pores (meshes) of 46 to 50/inch, a pore diameter of 0.4 to 0.6mm, and a specific surface area of 4500 to 5500m2/m3And a porous metal body having a thickness of 0.8 to 1.2 mm. The porous metal body is preferably made of aluminum when used as a positive electrode current collector, and is preferably made of copper when used as a negative electrode current collector.
When the porous metal body is made of aluminum, it can be produced by: after a carbon coating material was applied to a polyurethane foam having open cells and subjected to a conductive treatment, a carbon coating material was applied to a polyurethane foam having open cells in a ratio of 33: 67 molar ratio comprising 1-ethyl-3-methylimidazole chloride and aluminum chloride (AlCl)3) And a plating solution further containing a small amount of phenanthroline, forming a predetermined amount of an aluminum layer by plating in an inert atmosphere, and thermally decomposing the polyurethane foam and the carbon coating under the condition of inhibiting excessive oxidation of the aluminum surface in an oxygen-containing atmosphere at a temperature in the range of 500 to 660 ℃ to remove the aluminum layer. In addition, when the porous metal body is made of copper, it can be produced by: a carbon paint is applied to a polyurethane foam having open cells and subjected to a conductive treatment, a predetermined amount of a copper layer is formed by plating, the polyurethane foam and the carbon paint are thermally decomposed and removed, and then the oxidized copper layer is subjected to a reduction treatment in a hydrogen atmosphere. As the porous metal body thus produced, "Aluminum-Celmet" (registered trademark), copper or nickel available from Sumitomo electric industries, Ltd., can be used"Celmet" (registered trademark).
In the positive electrode active material 23, the thickness of the 1 st positive electrode active material 21 held on one surface of the current collector is preferably larger than the thickness of the 2 nd positive electrode active material 22 held on the other surface, and in the negative electrode active material 33, the thickness of the 1 st negative electrode active material 31 held on one surface of the current collector is preferably larger than the thickness of the 2 nd negative electrode active material 32 held on the other surface. In this case, specifically, the 1 st positive electrode active material 21 or the 1 st negative electrode active material 31 is preferably set to a thickness in the range of 100 to 250 μm, and the 2 nd positive electrode active material 22 or the 2 nd negative electrode active material 32 is preferably set to a thickness in the range of 50 to 150 μm.
In the lithium-ion secondary battery 1 of the present embodiment, the high-capacity active material contained in the 1 st positive electrode active material 21 is preferably Li (Ni)5/10Co2/10Mn3/10)O2、Li(Ni6/10Co2/10Mn2/10)O2、Li(Ni8/10Co1/ 10Mn1/10)O2、Li(Ni0.8Co0.15Al0.05)O2At least one selected from the group consisting of Li (Ni) can be used as the high-output type active material contained in the 2 nd positive electrode active material 221/6Co4/6Mn1/6)O2、Li(Ni1/3Co1/3Mn1/3)O2、LiCoO2、LiNiO2At least one selected from the group consisting of.
In the lithium-ion secondary battery 1 of the present embodiment, at least one selected from the group consisting of artificial graphite, natural graphite, Si, and SiO can be cited as the high-capacity active material contained in the 1 st negative electrode active material 31, and hard carbon or soft carbon can be cited as the high-output active material contained in the 2 nd negative electrode active material 32.
As the 1 st separator 4 or the 2 nd separator 5, a microporous film made of, for example, polyethylene, polypropylene, or the like can be used. The 1 st diaphragm 4 and the 2 nd diaphragm 5 may be composed of the same material as each other or may be composed of different materials.
Next, a method for manufacturing the lithium-ion secondary battery of the present embodiment will be described.
< production of Positive electrode >
First, Li (Ni) is used as a high-capacity active material5/10Co2/10Mn3/10)O2、Li(Ni6/10Co2/ 10Mn2/10)O2、Li(Ni8/10Co1/10Mn1/10)O2、Li(Ni0.8Co0.15Al0.05)O2At least one selected from the group consisting of polyvinylidene fluoride (PVDF) as a binder, and carbon black as a conductive aid, in a high-capacity type active material: adhesive: 80-99% of conductive auxiliary agent: 0.5-19.5: 0.5 to 19.5 in a mass ratio such that the total amount becomes 100, and diluting the mixture with an organic solvent such as N-methylpyrrolidone to prepare a 1 st positive electrode active material slurry.
Then, Li (Ni) is added as a high-output active material1/6Co4/6Mn1/6)O2、Li(Ni1/3Co1/3Mn1/3)O2At least one selected from the group consisting of polyvinylidene fluoride (PVDF) as a binder, and carbon black as a conductive aid, in a high-output type active material: adhesive: 80-99% of conductive auxiliary agent: 0.5-19.5: 0.5 to 19.5 in a mass ratio such that the total amount becomes 100, and diluting the mixture with an organic solvent such as N-methylpyrrolidone to prepare a 2 nd positive electrode active material slurry.
Next, the first positive electrode active material slurry is extruded from a nozzle at a predetermined pressure, for example, onto one surface of the current collector made of the porous metal body, and applied. Next, the collector made of the porous metal body coated with the slurry for the first positive electrode active material 1 is dried in the air at a temperature in the range of 90 to 130 ℃ for 0.5 to 3 hours. Then, the second positive electrode active material slurry is extruded from a nozzle at a predetermined pressure, for example, to coat the second surface of the current collector made of the porous metal body.
Next, the current collector made of the porous metal body coated with the slurry for the 1 st positive electrode active material and the slurry for the 2 nd positive electrode active material is dried in the air at a temperature in the range of 90 to 130 ℃ for 0.5 to 3 hours to form the positive electrode active material 23 made of the 1 st positive electrode active material 21 held on one surface of the current collector and the 2 nd positive electrode active material 22 held on the other surface, and the positive electrode active materials are rolled so as to have predetermined densities, respectively. Then, the positive electrode 1 is dried in vacuum at a temperature of 110 to 130 ℃ for 11 to 13 hours to obtain a positive electrode 2.
A 2 nd positive electrode 6 was produced in exactly the same manner as in the case of the 1 st positive electrode 2, except that only one of the 1 st positive electrode active material slurry and the 2 nd positive electrode active material slurry was applied to one surface of the current collector made of the porous metal body.
< production of negative electrode >
First, as a high capacity type active material, at least one selected from the group consisting of artificial graphite, natural graphite, Si, SiO, as a binder, at least one selected from the group consisting of carboxymethyl cellulose, styrene butadiene rubber, sodium polyacrylate, polyvinylidene fluoride, and carbon black as a conductive aid, in a high capacity type active material: adhesive: 80-99.5% of conductive auxiliary agent: 0.5-20: 0 to 10 by mass and 100 total amount, and diluting with an organic solvent such as N-methylpyrrolidone or pure water to prepare a 1 st negative electrode active material slurry.
Next, hard carbon as a high capacity type active material, at least one selected from the group consisting of carboxymethyl cellulose, styrene butadiene rubber, sodium polyacrylate, polyvinylidene fluoride as a binder, and carbon black as a conductive aid are mixed in the following ratio: adhesive: 80-99.5% of conductive auxiliary agent: 0.5-20: 0 to 10 by mass and 100 total amount, and diluting with an organic solvent such as N-methylpyrrolidone or pure water to prepare a 2 nd negative electrode active material slurry.
Next, a current collector made of the porous metal material was coated, dried in the air, rolled, and further dried in vacuum to obtain a 1 st negative electrode 3 or a 2 nd negative electrode 7, in the same manner as in the case of the 1 st positive electrode 2 or the 2 nd positive electrode 6 except that the 1 st negative electrode active material slurry and the 2 nd negative electrode active material slurry were used instead of the 1 st positive electrode active material slurry and the 2 nd positive electrode active material slurry.
< production of lithium ion Secondary Battery >
Next, the same number of 1 st positive electrodes 2 and 1 st negative electrodes 3 are alternately arranged with 1 st separators 4 or 2 nd separators 5 interposed therebetween, and 2 nd positive electrodes 6 are arranged at one end portions and 2 nd negative electrodes 7 are arranged at the other end portions. At this time, the 1 st positive electrode active material 21 of the 1 st positive electrode 2 faces the 1 st negative electrode active material 31 of the 1 st negative electrode 3 adjacent to the 1 st separator 4, and the 2 nd positive electrode active material 22 faces the 2 nd negative electrode active material 32 of the 1 st negative electrode 3 adjacent to the 2 nd separator 5.
In addition, when one end of the 1 st positive electrode 2 and the 1 st negative electrode 3 alternately arranged with the 1 st separator 4 or the 2 nd separator 5 interposed therebetween is the 1 st positive electrode active material 21 of the 1 st positive electrode 2, the 2 nd negative electrode 7 including the negative electrode active material 33 composed only of the 1 st negative electrode active material 31 is arranged with the 1 st separator 4 interposed therebetween at the end. In addition, when one end of the 1 st positive electrode 2 and the 1 st negative electrode 3 alternately arranged with the 1 st separator 4 or the 2 nd separator 5 interposed therebetween is the 2 nd positive electrode active material 22 of the 1 st positive electrode 2, the 2 nd negative electrode 7 including the negative electrode active material 33 composed only of the 2 nd negative electrode active material 32 is arranged with the 2 nd separator 5 interposed therebetween at the end.
On the other hand, when the other end of the 1 st positive electrode 2 and the 1 st negative electrode 3 alternately arranged with the 1 st separator 4 or the 2 nd separator 5 interposed therebetween is the 1 st negative electrode active material 31 of the 1 st negative electrode 3, the 2 nd positive electrode 6 including the positive electrode active material 23 composed of only the 1 st positive electrode active material 21 is arranged with the 1 st separator 4 interposed therebetween at the end. In the case where the other end of the 1 st positive electrode 2 and the 1 st negative electrode 3 alternately arranged with the 1 st separator 4 or the 2 nd separator 5 interposed therebetween is the 2 nd negative electrode active material 32 of the 1 st negative electrode 3, the 2 nd positive electrode 6 including the positive electrode active material 23 composed of only the 2 nd positive electrode active material 22 is arranged with the 2 nd separator 5 interposed therebetween at the end.
Next, the electrolytic solution is impregnated into the 1 st separator 4 and the 2 nd separator 5, and then the container is sealed so that the tabs 24 and 34 are exposed from the container, thereby producing the lithium ion secondary battery 1 of the present embodiment.
The electrolyte solution can be, for example, a solution obtained by dissolving LiPF in a solvent such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate at a concentration in the range of 0.1 to 3 mol/L, preferably 0.6 to 1.5 mol/L6、LiBF4、LiClO4And the like supporting the electrolyte.
Next, examples of the present invention and comparative examples are shown.
Examples
[ example 1 ]
In this example, first, as a collector composed of a metal porous body having a three-dimensional mesh structure in which columnar skeletons are connected three-dimensionally (hereinafter, simply referred to as "three-dimensional skeleton collector"), a collector composed of aluminum, having a porosity of 95%, a number of pores (meshes) of 46 to 50/inch, a pore diameter of 0.5mm, and a specific surface area of 5000m was used2/m3A current collector (Celmet (registered trademark) manufactured by Sumitomo electric industries, Ltd.) having a thickness of 1.0mm, a vertical length of 150mm and a horizontal length of 200mm was used as the 1 st positive electrode 2.
First, a slurry for the 1 st positive electrode active material containing a high capacity type active material was applied to a region 80mm in the vertical direction and 150mm in the horizontal direction in the center of one surface of the three-dimensional skeleton current collector. Next, a 2 nd positive electrode active material slurry containing a high-output type active material is applied to a region corresponding to the region to which the 1 st positive electrode active material slurry is applied, on the other surface of the three-dimensional skeleton current collector.
The above-described slurry for a positive electrode active material 1 was passed through with Li (Ni) as a high-capacity type active material5/10Co2/ 10Mn3/10)O2Polyvinylidene fluoride (PVDF) as a binder and carbon black as a conductive aid become high-capacity type active materials: adhesive: the conductive aid is 94: 2: 4 mass ratioThe resulting mixture was weighed and mixed with N-methylpyrrolidone to prepare a mixture. In addition, the above-mentioned 2 nd positive electrode active material slurry was passed through to make Li (Ni) as a high-output type active material1/6Co4/ 6Mn1/6)O2Polyvinylidene fluoride (PVDF) as a binder and carbon black as a conductive aid become high-output type active materials: adhesive: the conductive aid is 94: 2: 4, and mixed with N-methylpyrrolidone to prepare a mixture.
Next, the three-dimensional skeleton current collector having one surface coated with the 1 st positive electrode active material slurry and the other surface coated with the 2 nd positive electrode active material slurry was dried at a temperature of 120 ℃ for 12 hours in the air, then rolled, and further dried at a temperature of 120 ℃ for 12 hours in a vacuum.
Next, the electrode was punched out into a shape composed of a coating region 30mm in the vertical direction and 40mm in the horizontal direction to which the first positive electrode active material slurry 1 and the second positive electrode active material slurry 2 were applied, and a tab 24 15mm in the vertical direction and 30mm in the horizontal direction in contact with the coating region to which the first positive electrode active material slurry 1 and the second positive electrode active material slurry 2 were not applied, thereby obtaining a 1 st positive electrode 2.
The 1 st positive electrode 2 holds a 1 st positive electrode active material 21 formed of the 1 st positive electrode active material slurry on one surface of the three-dimensional skeleton current collector, and holds a 2 nd positive electrode active material 22 formed of the 2 nd positive electrode active material slurry on the other surface, thereby forming a positive electrode active material layer 23. In this example, the thickness of the 1 st positive electrode active material 21 held on one surface of the three-dimensional skeleton current collector was 0.225mm, and the bulk density was 3.2g/cm3The thickness of the 2 nd positive electrode active material 22 held on the other surface was 0.056mm, and the bulk density was 3.2g/cm3. In this example, two sheets of the 1 st positive electrode 2 were prepared.
In addition, a single sheet of the 2 nd positive electrode 6 is prepared, and the 2 nd positive electrode 6 holds the positive electrode active material 23 composed of only the 1 st positive electrode active material 21 formed from the 1 st positive electrode active material slurry on one surface of the three-dimensional skeleton current collector, in the same manner as in the case of the 1 st positive electrode 2, except that only the 1 st positive electrode active material slurry is applied on one surface of the three-dimensional skeleton current collector.
Next, a three-dimensional skeleton current collector made of copper and having a porosity of 95%, a number of pores (meshes) of 46 to 50/inch, a pore diameter of 0.5mm, and a specific surface area of 5000m was prepared2/m3A current collector (cellmet (registered trademark) manufactured by sumitomo electric industries co., ltd.) having a thickness of 1.0mm, a vertical length of 150mm, and a horizontal length of 80mm was used as the 1 st negative electrode 3.
First, a slurry for the 1 st negative electrode active material containing a high-capacity active material was applied to a region 70mm in the vertical direction and 70mm in the horizontal direction in the center of one surface of the three-dimensional skeleton current collector. Next, a 2 nd anode active material slurry containing a high-output type active material is applied to a region corresponding to the region to which the 1 st anode active material slurry is applied, on the other surface of the three-dimensional skeleton current collector.
The slurry for the negative electrode active material of the 1 st aspect is prepared by making natural graphite as a high-capacity active material, a mixture of carboxymethyl cellulose and styrene butadiene rubber as a binder, and carbon black as a conductive auxiliary agent into a high-capacity active material: adhesive: and (3) the conductive auxiliary agent is 96.5: 2.5: 1, and mixed with pure water to prepare the mixture. In addition, the above-described slurry for a negative electrode active material of the 2 nd above is prepared without using any conductive auxiliary agent at all so that hard carbon as a high-output type active material and polyvinylidene fluoride (PVDF) as a binder become a high-output type active material: 98 parts of binder: 2, and mixed with N-methylpyrrolidone to prepare a mixture.
Next, the three-dimensional skeleton current collector having one surface coated with the 1 st anode active material slurry and the other surface coated with the 2 nd anode active material slurry was dried at a temperature of 120 ℃ in the air for 12 hours, then rolled, and further dried at a temperature of 120 ℃ in a vacuum for 12 hours.
Next, a shape consisting of a coating region 34mm in the vertical direction and 44mm in the horizontal direction on which the first negative electrode active material slurry and the second negative electrode active material slurry were coated, and a tab 34 15mm in the vertical direction and 30mm in the horizontal direction in contact with the coating region on which the first negative electrode active material slurry and the second negative electrode active material slurry were not coated was punched out, thereby obtaining a 1 st negative electrode 3 of this example.
The 1 st negative electrode 3 holds a 1 st negative electrode active material 31 made of the 1 st negative electrode active material slurry on one surface of the three-dimensional skeleton current collector, and holds a 2 nd negative electrode active material 32 made of the 2 nd negative electrode active material slurry on the other surface, thereby forming a negative electrode active material 33. In this example, the thickness of the 1 st negative electrode active material 31 held on one surface of the three-dimensional skeleton current collector was 0.212mm, and the bulk density was 1.7g/cm3The second negative electrode active material layer 32 held on the other surface had a thickness of 0.082mm and a bulk density of 1.1g/cm3. In this example, two pieces of the 1 st anode 3 were prepared.
In addition, a single piece of the 2 nd negative electrode 7 is prepared, and the 2 nd negative electrode 7 holds the negative electrode active material 33 composed of only the 1 st negative electrode active material 31 formed of the 1 st negative electrode active material slurry on one surface of the three-dimensional skeleton current collector, just as in the case of the 1 st negative electrode 3, except that the 1 st negative electrode active material slurry is applied only on one surface of the three-dimensional skeleton current collector.
Next, in the bag of the aluminum laminate sheet, the 1 st positive electrode 2 and the 1 st negative electrode 3 are arranged so that the 1 st separator 4 or the 2 nd separator 5 is sandwiched between the 1 st positive electrode 2 and the 1 st negative electrode 3, and the tabs 24, 34 are exposed to the outside of the bag. Further, the 2 nd positive electrode 6 is disposed so as to sandwich the 1 st separator 4 between the adjacent 1 st negative electrode 3 at one end portion and expose the tab 24 to the outside of the pouch, and the 2 nd negative electrode 7 is disposed so as to sandwich the 1 st separator 4 between the adjacent 1 st positive electrode 2 at the other end portion and expose the tab 34 to the outside of the pouch. Then, the electrolyte solution is impregnated into the 1 st separator 4 and the 2 nd separator 5, and then the lithium-ion secondary battery 1 having the structure shown in fig. 1 is manufactured by vacuum sealing.
As the 1 st and 2 nd separators 4 and 5, a microporous film of polyethylene having a thickness of 15 μm was used. As the electrolyte, a mixture of ethylene carbonate, dimethyl carbonate and diethyl carbonate in a ratio of 40: 30: LiPF as a supporting electrolyte was dissolved in a mixed solvent mixed at a volume ratio of 30 at a concentration of 1.2 mol/L6The electrolyte of (1).
In the lithium ion secondary battery 1 of the present embodiment, the 1 st positive electrode active material 21 of the 1 st positive electrode 2 faces the 1 st negative electrode active material 31 of the 1 st negative electrode 3 or the 2 nd negative electrode 7 adjacent to each other through the 1 st separator 4, and the 2 nd positive electrode active material 22 faces the 2 nd negative electrode active material 32 of the 1 st negative electrode 3 adjacent to each other through the 2 nd separator 5. The 1 st negative electrode active material 31 of the 1 st negative electrode 3 faces the 1 st positive electrode active material 21 of the 1 st positive electrode 2 or the 2 nd positive electrode 6 adjacent to each other with the 1 st separator 4 interposed therebetween.
< calculation of energy Density >
Next, with respect to the lithium-ion secondary battery 1 produced in this example, the provisional capacity of the positive electrode at a temperature of 25 ℃ was calculated from the active material amounts of the 1 st positive electrode active material 21 and the 2 nd positive electrode active material 22. Next, a (0.2C) current value at which discharge was possible for 5 hours was determined based on the above-described provisional capacity.
Next, the lithium ion secondary battery 1 produced in this example was charged to 4.2V at a constant current of 0.2C, and after being charged at a constant voltage of 4.2V for 1 hour, was discharged to 2.4V at a constant current of 0.2C. The capacity at the time of the constant current discharge was defined as a rated capacity (mAh/g), and the energy density (Wh/g) was calculated from the following equation (1) by defining the voltage at the time of 1/2 capacity of the rated capacity as an average voltage (V) in a charge-discharge curve at the time of the constant current discharge.
Energy density (Wh/g) × rated capacity (mAh/g) × average voltage (V) · (1)
The results are shown in FIG. 3. Fig. 3 shows the energy density (Wh/g) of the lithium-ion secondary battery 11 of comparative example 1, which will be described later, as a ratio to 1.
< calculation of output Density >
Then, at a temperature of 25 ℃, in order to obtain a capacity with a charging rate (SOC) of 50% with respect to the rated current, the battery was charged at 0.2C for 2.5 hours, and the Open Circuit Voltage (OCV) at that time was measured) Is set to E0。
Next, the operation of charging the capacity corresponding to the discharge amount at 0.2C after discharging for 10 seconds at a predetermined current value and measuring the voltage at that time was repeated while changing the predetermined current value from 0.5C to 3.0C at every 0.5C. Then, the current value is plotted on the horizontal axis and the voltage with respect to each current value is plotted on the vertical axis, and the slope of the straight line obtained at this time is defined as the resistance R.
Then, the termination voltage E is setcutoffSet to 2.4V, using the resistor R and the open circuit voltage E0The output density W is calculated from the following expression (2).
W＝(|Ecutoff－E0|/R)×Ecutoff···(2)
The results are shown in FIG. 4. Fig. 4 shows the output density of the lithium-ion secondary battery of comparative example 1, which will be described later, as a ratio to 1.
< evaluation of durability: capacity retention ratio >
Next, the operation of charging to 4.2V at a constant current of 0.5C and discharging to 2.4V at a constant current of 0.5C with respect to the above rated capacity was set to 1 cycle, and the operation was repeated for 200 cycles at 45 ℃. Fig. 5 shows the change in capacity retention with respect to cycle number.
< evaluation of durability: resistance rise rate
For the lithium-ion secondary battery 11 produced in this example, the internal resistance before the start of the operation (0 cycle) and after 200 cycles was measured when the capacity retention rate was measured. The results are shown in FIG. 6.
[ comparative example 1 ]
As shown in fig. 2, the lithium ion secondary battery 11 of the present comparative example has a structure in which the same number of 1 st positive electrodes 12 and 1 st negative electrodes 13 are alternately adjacent to each other with separators 14 interposed therebetween, and a 2 nd positive electrode 16 is disposed at one end portion and a 2 nd negative electrode 17 is disposed at the other end portion.
The 1 st positive electrode 12 includes: a current collector 18 made of aluminum foil; and a positive electrode active material layer 23 composed of a 1 st positive electrode active material layer 21 containing a high capacity type active material on both surfaces of the current collector 18 and a 2 nd positive electrode active material layer 22 containing a high output type active material on the 1 st positive electrode active material layer 21 on both surfaces of the current collector 18, wherein a part of the current collector 18 exposed from the positive electrode active material layer 23 is a tab.
The 1 st negative electrode 13 includes: a current collector 19 made of copper foil; and a negative electrode active material layer 33 composed of a 1 st negative electrode active material layer 31 containing a high capacity type active material on both sides of the current collector 19 and a 2 nd negative electrode active material layer 32 containing a high output type active material on the 1 st negative electrode active material layer 31 on both sides of the current collector 19, and a part of the current collector 19 exposed from the negative electrode active material layer 33 is a tab.
The 2 nd positive electrode 16 has the same structure as the 1 st positive electrode 12 except that the positive electrode active material layer 23 is provided only on one surface of the current collector 18, and the 2 nd negative electrode 17 has the same structure as the 1 st negative electrode 13 except that the negative electrode active material layer 33 is provided only on one surface of the current collector 19.
The 1 st positive electrode active material layer 21 of the 1 st positive electrode 12 faces the 1 st negative electrode active material layer 31 of the 1 st negative electrode 13 or the 2 nd negative electrode 17 adjacent to each other with the separator 14 interposed therebetween, and the 1 st positive electrode active material layer 21 of the 2 nd positive electrode 16 faces the 1 st negative electrode active material layer 31 of the 1 st negative electrode 13 adjacent to each other with the separator 4 interposed therebetween.
In this comparative example, a lithium-ion secondary battery 11 having the structure shown in fig. 2 was manufactured as follows.
First, a positive electrode was produced as follows using an aluminum foil having a width of 20cm, a length of 1m, and a thickness of 15 μm.
First, a 1 st positive electrode active material slurry containing a high capacity type positive electrode active material was applied to a 10cm area in the central portion of the aluminum foil, dried at a temperature of 130 ℃ for 10 minutes, and then pressed with a load of 15 tons using a roll press at a temperature of 130 ℃ to form a 1 st positive electrode active material layer. The above-described first positive electrode active material slurry is prepared by mixing: adhesive: and (3) the conductive auxiliary agent is 95: 2.5: a positive electrode active material slurry was prepared in exactly the same manner as the slurry for the 1 st positive electrode active material in example 1, except that the weight ratio was 2.5.
Next, a 2 nd positive electrode active material slurry containing a high-output type positive electrode active material was applied on the 1 st positive electrode active material layer, dried at a temperature of 130 ℃ for 10 minutes, and then pressed with a load of 5 tons by a roll pressure at a temperature of 130 ℃ to form a 2 nd positive electrode active material layer. The above-mentioned 2 nd positive electrode active material slurry is a high-output type active material except that: adhesive: and (3) the conductive auxiliary agent is 95: 2.5: a positive electrode active material slurry of example 1 was prepared in exactly the same manner as in example 2 except that the slurry was weighed so as to have a mass ratio of 2.5.
Next, the aluminum foil was punched into a shape composed of a coating region 30mm in length and 40mm in width and a tab region 15mm in length and 30mm in width in contact with the coating region, thereby obtaining a positive electrode.
In this comparative example, the thickness of the 1 st positive electrode active material layer 21 in one surface of the current collector 18 was 0.042mm, and the bulk density was 3.30g/cm3The thickness of the No. 2 positive electrode active material layer 22 was 0.016mm, and the bulk density was 2.65g/cm3. In this comparative example, four pieces of the 1 st positive electrode 2 were prepared.
In addition, a 2 nd positive electrode 16 was obtained, and the 2 nd positive electrode 16 was provided with the positive electrode active material layer 23 only on one surface of the current collector 18 in exactly the same manner as the 1 st positive electrode 12 except that the positive electrode active material layer 23 was formed only on one surface of the current collector 18. In this comparative example, one sheet of the 2 nd positive electrode 16 was prepared.
Next, a copper foil having a width of 20cm, a length of 1m and a thickness of 8 μm was used to prepare a negative electrode as follows.
First, a 1 st anode active material slurry containing a high-capacity anode active material was applied to a 10cm area in the central portion of the copper foil, dried at 130 ℃ for 10 minutes, and then pressed with a 15 ton load using a roll press at 130 ℃. The slurry for the negative electrode active material of the 1 st aspect is prepared by making natural graphite as a high-capacity active material, a mixture of carboxymethyl cellulose and styrene butadiene rubber as a binder, and carbon black as a conductive auxiliary agent into a high-capacity active material: adhesive: and (3) the conductive auxiliary agent is 96.5: 2.5: 1, and mixed with pure water to prepare the mixture.
Next, a 2 nd negative electrode active material slurry containing a high-output type negative electrode active material was applied on the 1 st negative electrode active material layer, dried at a temperature of 130 ℃ for 10 minutes, and then pressed with a load of 5 tons by a roll press at a temperature of 130 ℃ to form a 2 nd negative electrode active material layer. The above-described slurry for a negative electrode active material of the 2 nd above is prepared by mixing hard carbon as a high-output type active material, carboxymethyl cellulose as a binder, and styrene butadiene rubber into a high-output type active material without using any conductive auxiliary agent: 98 parts of binder: 2, and mixed with pure water to prepare the mixture.
Next, the copper foil was punched into a shape consisting of a coating region 34mm in the vertical direction and 44mm in the horizontal direction and a tab region 15mm in the vertical direction and 30mm in the horizontal direction in contact with the coating region, thereby obtaining a negative electrode.
In this comparative example, the thickness of the 1 st negative electrode active material layer 31 was 0.039mm and the bulk density was 1.55g/cm on one surface of the current collector 193The 2 nd negative electrode active material layer 32 had a thickness of 0.024mm and a bulk density of 1.00g/cm3. In this comparative example, four pieces of the 1 st negative electrode 13 were prepared.
In addition, a 2 nd negative electrode 17 was obtained, and this 2 nd negative electrode 17 was provided with the negative electrode active material layer 33 only on one surface of the current collector 8, in the same manner as the 1 st negative electrode 13 except that the negative electrode active material layer 33 was formed only on one surface of the current collector 19. In this comparative example, one second anode 17 was prepared.
Next, in the bag of the aluminum laminate sheet, the 1 st positive electrode 12 and the 1 st negative electrode 13 are disposed with the separator 14 interposed between the 1 st positive electrode 12 and the 1 st negative electrode 13, and the tabs are exposed to the outside of the bag. Further, the 2 nd positive electrode 16 is disposed at one end portion so as to sandwich the separator 14 between the adjacent 1 st negative electrode 13 and expose the tab to the outside of the pouch, and the 2 nd negative electrode 17 is disposed at the other end portion so as to sandwich the separator 14 between the adjacent 1 st positive electrode 12 and expose the tab to the outside of the pouch. The separator 14 is impregnated with the electrolyte solution, and then vacuum-sealed, thereby producing the lithium-ion secondary battery 11 having the structure shown in fig. 2.
As the separator 14, a microporous film made of polyethylene having a thickness of 15 μm was used. As the electrolyte, a mixture of ethylene carbonate, dimethyl carbonate and diethyl carbonate in a ratio of 40: 30: LiPF as a supporting electrolyte was dissolved in a mixed solvent mixed at a volume ratio of 30 at a concentration of 1.2 mol/L6The electrolyte of (1).
The lithium ion secondary battery 11 of this comparative example was a lithium ion secondary battery having the same capacity as the lithium ion secondary battery 1 of example 1.
Next, the energy density and the output density were calculated in exactly the same manner as in example 1, except that the lithium-ion secondary battery 11 obtained in this comparative example was used. The energy density is shown in fig. 3 and the output density is shown in fig. 4.
Next, the durability was evaluated in exactly the same manner as in example 1, except that the lithium-ion secondary battery 11 obtained in this comparative example was used. Fig. 5 shows the change of the capacity retention rate with respect to the number of cycles, and fig. 6 shows the internal resistance before the start of the operation (0 cycle) and after 200 cycles when the capacity retention rate was measured with respect to the resistance increase rate.
From fig. 3 to 6, it is clear that the lithium-ion secondary battery 1 of example 1 is excellent in both energy density and output density and also in charge-discharge cycle characteristics, compared to the lithium-ion secondary battery 11 of comparative example 1.
In addition, according to the lithium-ion secondary battery 1 of example 1, the weight per unit area of the cathode active material layer 23 or the anode active material layer 33 per average electrode can be increased by using the above-described three-dimensional skeleton collector. Therefore, according to the lithium-ion secondary battery 1 of example 1, the number of electrodes can be reduced as compared with the lithium-ion secondary battery 11 of comparative example 1, and the mass of the lithium-ion secondary battery can be reduced, so that the energy density can be improved.
Description of the reference numerals
1 … lithium ion secondary battery, 2 … 1 st positive electrode, 3 … st negative electrode, 6 … nd positive electrode, 7 … nd negative electrode, 2 nd negative electrode, 21 … st positive electrode active material, 22 … nd positive electrode active material, 23 … positive electrode active material, 31 … st negative electrode active material, 32 … nd negative electrode active material, 33 … negative electrode active material.

Claims (3)

1. A lithium ion secondary battery having a structure in which at least one positive electrode and at least one negative electrode are alternately adjacent to each other with a separator interposed therebetween,
the positive electrode includes: a positive electrode current collector composed of a porous metal body having a three-dimensional mesh structure; a 1 st positive electrode active material containing a high capacity type active material held on one surface of the positive electrode current collector; and a 2 nd positive electrode active material containing a high-output type active material held on the other surface of the positive electrode current collector,
the negative electrode includes: a negative electrode current collector composed of a porous metal body having a three-dimensional mesh structure; a 1 st negative electrode active material containing a high-capacity type active material held on one surface of the negative electrode current collector; and a 2 nd negative electrode active material containing a high output type active material held on the other surface of the negative electrode current collector,
the 1 st positive electrode active material faces the 1 st negative electrode active material adjacent to the 1 st positive electrode active material with the 1 st separator interposed therebetween, and the 2 nd positive electrode active material faces the 2 nd negative electrode active material of the negative electrode adjacent to the 2 nd positive electrode active material with the 2 nd separator interposed therebetween.
2. The lithium ion secondary battery according to claim 1,
the 1 st positive electrode active material contains Li (Ni)5/10Co2/10Mn3/10)O2、Li(Ni6/10Co2/10Mn2/10)O2、Li(Ni8/10Co1/10Mn1/10)O2、Li(Ni0.8Co0.15Al0.05)O2At least one selected from the group consisting of,
the 2 nd positive electrode active material contains Li (Ni)1/6Co4/6Mn1/6)O2、Li(Ni1/3Co1/3Mn1/3)O2Selected from the group consisting ofAt least one of (1).
3. The lithium ion secondary battery according to claim 1,
the 1 st negative electrode active material contains at least one selected from the group consisting of artificial graphite, natural graphite, Si, and SiO,
the 2 nd anode active material contains hard carbon.
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